Typical connection technologies for cables and in particular copper cables comprise crimping. Crimping is joining two pieces of metal or other ductile material by deforming one or both of them to hold each other. The bend or deformity is called the crimp. Typically, the metals are joined together via a special connector. The stripped cable that is often stranded, is inserted in an opening, such as a crimp portion, of the contact terminal. Then, a crimper is used to tightly squeeze the opening (i.e. the crimp portion) against the stripped cable.
Depending on the type of contact terminal used, the contact terminal may be attached to a metal plate or the like by a separate screw or bolt or the contact terminal could be simply screwed on using the contact terminal itself. Known crimp connections provide an electrical conductive connection that is able to withstand a certain amount of pullout force. The pullout force is typically understood as the force that is needed to pull out the stripped cable end from the crimping portion of the contact terminal in the longitudinal direction. The longitudinal direction is the direction of the cable axis.
However, in particular when using copper cables, crimp connections provide only a low protection against fretting corrosion. Fretting corrosion is a damage that occurs at the contact surfaces of the crimping portion of the contact terminal on the one hand, and at the contact surfaces of the stripped cable end on the other hand. This damage is induced under load, such as mechanical stress. The mechanical stress can e.g. be induced by the crimping itself and in the presence of repeated relative surface motion, as for example vibrations.
These vibrations can be a micro-movement between the outer strands of the cable end and the inner surface of the contact terminal. Typically, the relative sliding (micro) motion is in the range from certain nanometers to micrometers. The occurring fretting corrosion causes high and unstable ohmic resistance values of the crimped connection after a particular short time of use.
Further, the mechanical durability and in particular the pullout force that the crimp connection is able to withstand will be reduced due to fretting corrosion. Thus, there is a need in the art to improve conventional crimp connections in order to prevent fretting corrosion and to increase the pullout force that the crimp connection is able to withstand.